In an optical video disk player of a so-called compatible type, the information stored on a compact disk an be reproduced. FIGS. 2 and 3 are sectional views of a video disk mounting approach for an optical video disk player. A centering hub 2 having two conical portions 3 and 4 is mounted at a central portion of a turntable 1. The conical portion 3 comes into contact with an inner circumference of a video disk 6 when the video disk 6 is mounted, while the conical portion 4 comes into contact with an inner circumference of a compact disk 7 when the compact disk 7 is mounted, thereby performing centering of the disk. During the mounting of a compact disk 7, the centering hub 2 is made to descend or depress into the inside of the turntable 1 as can be seen in FIG. 3. A stopper 5 is arranged so that the distance D from the lower end of the stopper 5 to the turntable 1 is set to be substantially equal to the sum of the thickness of the video disk 6 and that of the compact disk 7.
In the event the video disk 6 is mounted while the compact disk 7 is left on the turntable 1, the video disk 6 comes into contact with the stopper 5 to increase the load of the turntable 1 so that the turntable 1 becomes impossible to rotate. Thus, a mechanical stopper approach is utilized to prevent operation of the video disk player when there is a double mounting of disks.
As described above, the stopper 5 is arranged so as to come into contact with the video disk 6. However, the stopper 5 does not make contact and does not operate as a stopper if the distance D is set to be unsuitably large, while, on the contrary, the stopper 5 acts as an obstruction and it becomes difficult to mount a disk if the distance D is set to be unsuitably small. In the latter situation, there exists a danger that the excessively loaded disks will become damaged due to excessive mechanical contact between the disks and excessive mechanical contact between a disk and the mechanical stopper. Accordingly, in order to utilize the above-described mechanical stopper approach, it is necessary to accurately determine and adjust the distance D during manufacturing, resulting in an increased burden on manufacturing and increased manufacturing costs.